Technical Field
The following description relates to one or more aspects of an image reader, and a method and a computer-readable medium therefor.
Related Art
An image reader has been proposed that is configured to read an image of a document sheet by emitting light onto the document sheet and receiving reflected light from the document sheet by an image sensor. The image sensor is configured to generate electrical charges responsive to a quantity of the received light and output image signals based on the generated charges. Nevertheless, even when not receiving any light, the image sensor generates electrical charges and an electrical current. Such an electrical current, generated due to the electrical charges generated by the image sensor when the image sensor does not receive any light, is referred to as a dark current. The dark current has a negative influence, as a noise, on the read image. Therefore, various techniques to remove the influence of the dark current have been proposed. For instance, an image reader has been known that is configured to remove the influence of the dark current by acquiring white reference data based on reflected light from a white reference plate and black reference data based on reflected light from a black reference plate and performing shading correction based on the white reference data and the black reference data.